I think those social media updates are part and parcel of bounties, so they have to be posted--correct me if I'm wrong, because I've never participated in one, but my understanding is that this is how people show they've participated.
An even better solution would be for ALL of these bounties to have their own website, and not one that has anything to do with bitcointalk. This forum isn't necessary for that at all. Signature campaigns, maybe, but not FB & Twitter.